1. Field of the Invention
The present invention relates to a printing apparatus for making plates by recording and developing images on the plates, and thereafter printing the images by feeding ink to the plates. The invention relates also to a method of developing plates for use in the printing apparatus.
2. Description of the Related Art
In an ordinary conventional printing apparatus, a prepress process is carried out first to make a plate by exposing the plate placed in contact with a film having a binarized black and white image recorded thereon. Then, the plate is loaded into the printing apparatus to carry out a printing process.
Recently, printing apparatus commonly called digital printers have been proposed, one such printer being capable of performing both the prepress process and printing process. The digital printers employ a "computer-to-plate" system for forming images on plates by directly scanning and exposing the plates with laser beams or the like modulated with image signals.
Such printing apparatus are described in Japanese Patent Publication (Unexamined) H9-141821 (1997), Patent Publication (Unexamined) H9-123402 (1997) and Patent Publication (Unexamined) H9-131855 (1997), for example. Each of the printing apparatus described in these publications has an image recorder for recording images on a plate mounted peripherally of a cylinder such as a plate cylinder, an impression cylinder or a plate-making cylinder. In parallel with the image recording process, a developing process is carried out by placing a developing roller with the plate for applying a developer to the plate.
Since such conventional printing apparatus perform the image recording and developing processes concurrently, the turning angle velocity of the cylinder is dependent on the processing speed of the image recorder. The developing time from application of the developer to the plate to removal of the developer therefrom is determined by the processing speed of image recorder.
Consequently, the plate developing time does not agree with the time required for the developer to develop the plate. This could result in a failure to develop the plate properly, i.e. an overdevelopment or underdevelopment of the plate.